In a world where sharing a photo is strictly a matter of getting another copy made and mailing it, or getting it published, copyrights are pretty easy to keep track of and these laws hold up pretty well. Sending a physical photo to your grandmother goes like this: you either put the picture in an envelope and send it, or you get a copy made yourself and send that.

Sending your grandmother an email photo, though, might involve copying your photo five or six times; first to Google’s servers, then to another server, then to an ISP’s CDN, then to AOL’s servers, then to your grandmother’s computer. As far as you’re concerned, this feels exactly like dropping an envelope in the mail. As far as copyright is concerned, it’s a choreographed legal dance.

And so these sites have to get your permission — a license — to copy and distribute the things you post. Just to function as advertised, they need your permission to “use” and to “host,” to “store” and “reproduce.” What they don’t necessarily need is the right to “modify” and “create derivative works,” or to “publicly perform.” That is, unless they need to make money. Which of course they do.